1. Field of the Invention
The present invention relates to a transfer printer in which ink on a transfer ribbon in contact with printing paper is transferred to the paper by means of a print head, thereby effecting printing.
2. Description of the Related Art
Transfer printers are used, for example, as label printers for printing item names, bar codes, etc. on labels. The label printer comprises a printing section which includes a platen roller and a line thermal head adapted to be pressed against the roller. A supply shaft and a take-up shaft for a transfer ribbon are located over the printing section. When the take-up shaft is rotated by means of a motor and the like, the transfer ribbon is fed out from the supply shaft, transported past a guide shaft and the printing section, and taken up by means of the take-up shaft. The supply shaft is connected with a load mechanism. A desired back tension is applied to the transfer ribbon by damping the rotation of the supply shaft by means of the load mechanism.
Conventionally, attaching and detaching operations for replacing the transfer ribbon must be performed in a narrow space within the printer body, while avoiding interfering with other components, so that the working efficiency is not very high. Similarly, the thermal head must be attached or detached for replacement or cleaning in a narrow slice within the printer body, while avoiding interfering with the other components, so that the working efficiency is low.
Thereupon, a printer of a novel design has recently been developed to facilitate the replacement of the transfer ribbon. In this printer, a supply shaft and a take-up shaft wound with a ribbon are housed in a casing to form a modular structure or unit, which is removably mounted in the body of the printer. According to this arrangement, the transfer ribbon can be replaced outside the printer by removing the unit from the printer body. Also, a printer is proposed in which a thermal head is supported so that it can be drawn out of the printer body.
If the transfer ribbon and the supply and take-up shafts are combined into the unit, the replacement of the ribbon itself can be facilitated indeed. Nevertheless, the ribbon unit must be attached to or detached from the printer in the narrow space within the printer body, so that the working efficiency is not satisfactory.
If the ribbon unit and the thermal head are arranged so as to be removable from the printer body, they are lower in mounting strength than fully fixed ones, and will shake in the printer body during printing operation. Thus, the transfer ribbon may meander or be wrinkled, so that high print quality cannot be ensured.